The present invention relates to compressors. More particularly the present invention relates to a discharge valve incorporating a contoured discharge valve disc.
Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps which are caused to orbit relative to one another so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided to cause the relative orbiting scroll movement.
Because scroll compressors depend upon successive chambers for suction, compression, and discharge processes, suction and discharge valves in general are not required. However, the performance of the compressor can be increased with the incorporation of a discharge valve. One of the factors that will determine the level of increased performance is the reduction of what is called the recompression volume. The recompression volume is the volume of the discharge chamber and discharge port of the compressor when the discharge chamber is at its smallest volume. The minimization of this recompression volume will result in a maximizing of the performance of the compressor.
In addition, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of a power interruption, there is a strong tendency for the backflow of compressed gas from the discharge chamber and to a lesser degree for the gas in the pressurized chambers to effect a reverse orbital movement of the scroll members and any associated drive shaft. This reverse movement often generates noise or rumble, which may be considered objectionable and undesirable. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power interruption be experienced. This reverse operation may result in overheating of the compressor and/or other inconveniences to the utilization of the system. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the forward direction. However, the discharge pressure will again increase to a point where the drive motor is stalled and the cycle is repeated. Such cycling is obviously undesirable. The incorporation of a discharge valve can reduce or eliminate these reverse rotation problems.
Traditional discharge valves include a flat disc that is operable between an open and a closed position for selectively enabling the flow of pressurized gas through the discharge valve. As a result of the pressure differential on either side of the flat disc the flat disc experiences significant, cyclical tensile stresses. Over time, these stresses may fatigue the flat disc and result in failures. To cope with these stresses, flat discs generally have a thicker profile and thus are heavier than desired. Increased weight results in slower response time as the disc moves between its open and closed positions.
Therefore, it is desirable in the industry to provide a discharge valve assembly having an improved disc design. The improved disc design should reduce the tensile stresses the disc experiences due to pressure differentials and preferably improve the flow through the discharge valve for lowering the pressure differential, thereby lowering the experienced tensile stress. Further, in reducing the tensile stresses, the improved disc design should have a thinner profile, thereby reducing the weight of the disc and improving response of the disc to pressure changes.
In a first embodiment, the present invention resides in the provision of a contoured disc valve in a scroll compressor, and in an alternative embodiment in a conventional single-vane rotary compressor.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.